Iolite is a version of Cordierite which is a silicate mineral found in metamorphic and igneous rocks. Cordierite has a chemical composition of (Mg,Fe)2Al4Si5O18 and forms a solid solution series with sekaninaite which has a chemical composition of (Fe,Mg)2Al4Si5O18. Cordierite was known as 'dichroite' and 'water sapphire'. Dichroite means "two-color rock," inspired by cordierite's pleochroic property. These gems show two or three colors when viewed from different areas.
Species: variety of cordierite ♦ Chemistry: (Mg,Fe)2Al4Si5O18 ♦ Color: blue to violet, clear, gray or yellow ♦ Cleavage: fair to poor ♦ Transparency: transparent to translucent ♦ Luster: vitreous, greasy ♦ Crystal System: orthorhombic ♦ Moh's Hardness: 7-7.5 ♦ Localities: Australia, Brazil, Burma, Canada, India, Madagascar, Namibia, Sri Lanka, Tanzania and the United States.